Cable television (CATV) networks supply high frequency “downstream” signals from a main signal distribution facility, known as a “headend,” through the CATV network infrastructure, to the homes and offices of subscribers The downstream signals are supplied to the subscriber equipment, such as television sets, telephone sets and computers, to enable them to operate.
In addition, most CATV networks also transmit “upstream” signals from the subscriber equipment back to the headend of the CATV network. For example, a set top box enables the subscriber to select a TV program for display on the television set by transmitting the program selection to the CATV provider. Upstream signals are sent from the set top box to the headend signal-delivering equipment. This equipment responds by transmitting the selected downstream signal to the subscriber. As another example, two-way communication occurs when using a personal computer connected through the CATV infrastructure to the public Internet. As a further example, voice over Internet protocol (VOIP) telephone enabled devices use the CATV infrastructure and the public Internet as the medium for transmitting two-way telephone conversations. Such two-way signal transmission (upstream and downstream) is therefore an important feature for modern CATV networks.
Passive-active network interface devices have been developed to provide both passive and active, i.e. amplified, signals at the subscriber premises for the two different types of subscriber devices which operate from passive and active signals. Such passive-active network interface devices include a signal splitter which essentially divides or branches the incoming, or “downstream,” signals from the cable network into passive and active branches. The passive branch downstream signals are conducted through a passive branch of the network interface device without amplification or modification and applied to those subscriber devices which require passive signals for operation, such as, for example, a voice modem for a telephone set. The active branch downstream signals are conducted to an active signal conditioner, such as an amplifier, of an active branch of the network interface device. The active signal conditioner amplifies the strength of the signals or modifies some characteristic of the signals before the amplified, or conditioned, signals are delivered to one or more subscriber devices. The amplified signals are applied to those subscriber devices that benefit from the amplified signals, such as a television sets and computers.
The known passive-active interface devices have several disadvantages. They include electromechanical, moving parts. The moving parts can cause higher instances of failure or require undesirable levels of repair and maintenance. Also, the complexity of the known passive-active interface devices is associated with a relatively high manufacturing cost which, in turn, leads to a higher price passed along to the users of cable network services.
The high-frequency signals conducted through the cable network are susceptible to distortion from a number of sources. It is for this reason that coaxial cables are widely used to shield the high-frequency signals from degrading influences of the ambient environment. One requirement for maintaining high-quality signal conduction in a coaxial cable is properly terminating the coaxial cable. An improper termination causes reflections of the incident signals back into the transmission path. The reflections cause degradation of the desired incident signals received by the subscriber. The degradations are exemplified by amplitude ripple, group delay ripple, latency, and other similar effects which distort or reduce the incident signals. The signal reflections cause the subscriber to experience a degraded quality of service, or in some cases the level of degradation may prevent the subscriber from receiving meaningful service.
Therefore, there is a need to overcome, or otherwise lessen the effects of, the disadvantages and shortcomings described above.